The present invention provides a novel method and apparatus for extracting water from atmospheric air. The invention is particularly suited for implementation in hot, relatively arid areas of the world, where ground sources of fresh water are limited or where the production and transportation of fresh water involves great difficulties or considerable expense.
Various methods of extracting water from atmospheric air are known; however, the known methods have not been economical, in that the devices utilizing these methods require relatively costly energy sources in order to run efficiently and are mostly limited to a single cycle of operation within each 24 hour period utilizing the temperature differentials between night and day.
U.S. Pat. No. 4,285,702 describes a method of recovering water from atmospheric air by letting cool night air pass in one direction through an adsorber filled with water-adsorbing material, and during the day time reversing the flow of the air, after it has been heated, thereby drying the adsorbing material and condensing the water vapor. During the desorption phase, two closed air flows are formed, which are passed through the heating device and the adsorbing material multiple times. This method is limiting, in that it can be implemented primarily in the framework of a day-night cycle, and is not energy-efficient, requiring heating to relatively high temperatures during the desorption phase.
The present invention overcomes the drawbacks of the known methods of extracting water from atmospheric air. It provides a mode of extracting water from atmospheric air at any time of day or night, is not dependent upon temperature differentials between the cooler air at night and the warmer air during the day, and is energy-efficient, operating at substantially lower temperatures than is possible utilizing known methods and devices. The present invention makes it possible to extract water vapors from the atmospheric air in relatively simple, inexpensive industrial plants, or in smaller portable devices, without requiring significant inputs of energy. The condensation of water vapor according to the present invention can be done at any temperature of the ambient air, and it does not involve the use of chemicals or other substances that may be ecologically harmful.
There is therefore provided, in accordance with the present invention, a method for extracting water from atmospheric air, the method comprising the steps of:
(a) causing ambient air to be drawn across a sorbent material adapted to adsorb and/or absorb water vapor, the sorbent material being disposed in an enclosure comprising a first area containing the sorbent material and a second area containing a condenser;
(b) hermetically sealing the enclosure from the atmosphere, after the sorbent material has been fully saturated with water vapor;
(c) causing desorption of the water vapor from the sorbent material by heating the sorbent material, raising thereby the internal pressure of the enclosure;
(d) creating a partial vacuum in the enclosure and a pressure differential between the first area and the second area, by venting residual air and an amount of water vapor from the enclosure, so that water vapor flows from the first area to the condenser in the second area; and
(e) collecting the water which condenses on the condenser.
In accordance with a preferred embodiment of the invention, the sorbent material may be a solid or a liquid which is cooled during step (a) by ambient air drawn through conduits physically in contact with the sorbent material.
In accordance with a further embodiment of the invention, the water vapor which is vented in step (d) flows to a second condenser and the water which condenses thereon is collected together with the water from step (e).
There is also provided, in accordance with the present invention, apparatus for extracting water from atmospheric air, the apparatus comprising:
(a) an enclosure having first and second areas and adapted to be alternatively open to atmospheric air and hermetically sealed from atmospheric air;
(b) a sorbent material, adapted to adsorb and/or absorb moisture from the air, disposed within the first area and a condenser mounted within the second area;
(c) means for drawing ambient air across the sorbent material when the enclosure is open to atmospheric air;
(d) means for alternately cooling and heating the sorbent material;
(e) means for creating a partial vacuum within the enclosure and a pressure differential between the first and second areas; and
(f) a water collector adapted to collect the water that condenses on the condenser,
and the apparatus is characterized by having means for creating a partial vacuum within the enclosure, the means is a pressure-sensitive valve which opens when the internal pressure of the enclosure exceeds a pre-determined threshold.
In accordance with a preferred embodiment of the invention, the sorbent material is either a solid or a liquid and the means for cooling and heating comprise a system of conduits in physical contact with the sorbent material and in which flows ambient air.
In accordance with another embodiment of the invention, the apparatus also comprises a second condenser which communicates with the enclosure via the pressure-sensitive valve and a second water collector adapted to collect the water that condenses on the second condenser.